'Human transmission' of bird flu

A deadly strain of avian flu may have passed between people for the first time, experts believe.The avian influenza A (H7N9) virus is thought to have been transmitted between father and daughter in eastern China.

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Dr Peter Horby, senior clinical research fellow at the Oxford University Clinical Research Unit in Hanoi, Vietnam, said avian flu strains have been around for more than a decade, but "have not progressed any further down the path towards a pandemic virus".

He added: "Limited human-to-human transmission of H7N9 virus is therefore not surprising, and, like H5N1, H7N7, and H3N2v, does not necessarily represent the early stages of a trajectory towards full adaptation to humans."

Dr Horby said, however, that intensive surveillance was needed, including of the dose of virus needed to infect people and the role of repeated exposure to the strain.

The findings provide the strongest evidence yet of H7N9 transmission between humans, but its ability to transmit itself is "limited and non-sustainable," the experts believe.Researchers presented evidence on the strain, which emerged in eastern China in February.